Hydraulic lash adjuster



March 16, 1954 E. B. ETCHELLS HYDRAULIC LASH ADJUSTER Filed May 1951 nncntor ttorne Patented Mar. 16, 1954 UNITED STATES PATENT OF F-I-CE :HYDRAUIJIC LASH ADJ U S TER to General. Motors "001 "a corporation of De'law poration, Detroit, Mich., are

Application May .22, 1951, Serial N 0. 227,649

Claims. 1

Thi invention relate to .internal combustion engines generally and particularly to hydraulic lashadjusters such as are used in the valve operating linkages of such engines to maintain zero lash between the valve and the valve operating cam.

In the conventional hydraulic lash adjuster of this general type the motion of the cam is transmitted to the valve or valve push rod through .a cylinder and slidably interfiitted piston resting on a body of hydraulic fluid contained in the cylinder. The fluid used is theengine lubricating oil and is supplied to the lash adjuster by the engine oil pump. The amount of fluid introduced into the lash adjuster cylinder is automatically controlled by suitable valving withintheadjuster in accordance with the thermal expansion and wear occurring in the various parts of the valve linkage to maintain a zero lash in the system. In addition to thrustably supporting the lash adjuster piston in its cylinder, the engineoil fluid serves to lubricate the piston and cylinder walls. Because the engine oil commonly used contains one or more ingredients which tend to form varnish-like deposits on metal surfaces at temperatures normally encountered in engine operation, difficulty has been experienced with such deposits forming on the sliding surfaces of the lash -=adjuster vpiston and cylinder bore "with interference in its normal operation. One of the objects of the instant invention i to incorporate in such lash adjusters suitable means to prevent these varnish-like deposits from accumulating on such sliding metal surfaces.

.In one form of hydraulic lash adjuster of the aforementioned type, the thrust transmitting fluid body between the cylinder and pistonis :replenished as necessary from a fluid reservoir provided interiorl-y of the piston :and in communication With said body through a checkva-lve =.controlled passage in the piston. To maintain :the reservoir at a proper fluid level, engine .oil is fed thereto through cooperating ports in the side walls of the piston and cylinder. conventional practice in this respect has been to provide a singlesuch port in both the pistonand cylinder and to insure communication betweenthese por ts by means of anann-ular groove encircling the piston and formed either in the outer wall of "the piston or in the bore of the cylinder. This groove frequently has been found to fillwith'sludgaresulting .instoppage of fluid supply to the lash ad.- juster and its ultimate .inoperativeness. .l. have found that by increasing the number and preferably also the size of the side ports in the piston resultant open cup which is of the lash adjuster cylinder .2 and cylinder, the groove and its attendant disadvantages can be eliminated, and that the port defining edges may bev utilized as means forscraping and maintaining the-mutually slidingsurfaces of the :pistonand cylinder free of varnish-likedeposits.

The means by which theseand other objects of my invention are accomplished will be readily apparent from the following description having reference to the drawing wherein:

Figure 1 is a sectional view of a portion of an internal combustion engine showing-a valve operatin linkage including one .form of my improved hydraulic lash adjuster.

Figure 2 is an enlarged view similar to Figure 1 showing the details of the hydraulic lash adjuster illustrated therein,

Figure 3 is asectional view ofline 3-3 of -Eigure 2.

Figure 4 is a viewsim-ilar to Figure 2 but showing a modification of my improved lash adjuster.

Figure 5 ista sectional view taken on line -5-5 of Figure 4.

Referring now in detail. to the drawings and particularly Figures 1-3 thereof, the numeral 1 designates generally the frame of an internal combustion engine having one or more cylinders in each of which .is fit'ted with a reciprocating piston 3. Reciprocally mounted in the cylinder head 4 above the piston 3 is shown a poppet valve 5 which, in conventional. manner, controls the inlet (or exhaust) for the-cylinder 2. The valve-5 is normally held in closed position as shown by the valve spring 5., and-during engine operation is intermittently moved-downwardly to its open-position in opposition to the spring by the valve operating cam 7 whose motion is transmitted. to the upper end 18 of the valve through my thydra-ulic lash adjuster 9, push rod it and valve rocker 14. Except as hereinafter described, the lash adjuster S3 i's-of conventional form and serves to take up all clearance flash) between the cam land the 'valve end 3. Oil fromthe engine lubricating system is pumped by means, not shown, to the lash adjuster 9 through the oil gallery ll in the frame 7! and serves as the hydraulic fluidfor effecting the necessary lineal adjustments within the lash adiuster to carry out its .function of taking up lash in the valve train.

As shown in Figure 2 the lash adjuster 9 -comprises a cylinder it in the 'form of an upwardly laterally snpportedfor sliding .tappet bore .14 formed in the Slida'ely received in. the :bore 14 I 3 is a plunger or reciprocation in a engine frame 1.

piston l5 also of cup shape whose upper end is closed by a plug It on which rests the lower end of the push rod H3. The opposite end of the piston L5 is closed except for a passage H which connects the interior of the piston with the chamber l8 in the lower end of the cylinder. The ball l9 functions as a check valve controlling this passage l1 and is retained with limited operating clearance on the lower end of the piston by the valve cage 20. The cage 29 is in the form of an upright cup whose side walls are flanged outwardly at their upper ends and abut the shoulder 2| on the bottom of the piston, and whose end wall is perforated at 22 to allow fluid which enters the cage 23 from the passage l1 to pass into the chamber it. A downward extension 23 of the bottom end of the piston l3 projects into the cage 20 and serves to laterally support the same in place and to provide a seat for the ball valve l9 when closing the passage l1. Compressed between the flanged upper end of the cage 20 and the bottom of the chamber I8 is a coil spring 24 which serves dually to hold the cage in place on the piston and to urge the piston upwardly in the cylinder i3. Maximum travel of the piston in its cylinder is limited at the upper end by the cylinder supported retainer member 4B which serves as an abutment for the piston plug :6, and at the lower end by the shoulder 4| on the cylinder which serves as an abutment for the piston shoulder 2|.

The outer circumference of the cylinder |3 is provided with an annular groove 25 of sufiicient width to maintain communication with the oil gallery l2 throughout the range of reciprocation of the lash adjuster cylinder. Adjacent the upper end of the groove 25 there is provided a side port 26 extending through the wall of the lash adjuster cylinder and communicating at its inner end with an annular groove 21 encircling the periphery of the lash adjuster piston I5. As in the case of the groove 25 the piston groove 21 is of suflicient width to maintain communication with the cylinder port 26 throughout the range of reciprocation of the lash adjuster piston I5 relative to its cylinder I3. Interconnecting the piston groove 21 and the interior of the piston I3 is a side port 28 extending through the Wall of the lash adjuster piston. By this system of ports, grooves and passages engine lubricating oil from the gallery l2 may enter the chamber l8 and form therein a thrust transmitting body of fluid for supporting the lash adjuster piston in its cylinder during engine operation. Additional oil will fill the interior of the piston which serves as a reservoir for replenishing the body of fluid in the chamber [8.

During operation as the cam 1 raises the lash adjuster piston l3 the oil in the chamber l8 acts as a fluid body to simultaneously raise the lash adjuster piston, and the upward movement of the piston is transmitted through the plug It to the push rod l0 and thus through the rocker H to open the engine valve 5. During this movement a certain amount of fluid from the chamber I8 is permitted to leak past the lash adjuster piston, and this leakage fluid travels up the clearance between the piston and cylinder to the piston groove 21 from whence it is returned through the port 28 to the interior of the piston. Since the engine lubricating oil which serves as this fluid contains a certain amount of foreign matter in the form of suspended carbon particles and other grit, it frequently happens that the piston groove 21 eventually becomes filled with sludge, blocking communication between the ports 26 and 28 and rendering the lash adjuster inoperative. Also, since commercial oils used for engine lubrication generally have a tendency to form hard varnish deposits under engine operating temperature conditions, it frequently happens that such varnish deposits occur on the bore M of the lash adjuster cylinder and on the outer circumference of the lash adjuster piston l5 with resultant sticking of the piston in its cylinder. This sticking condition has been found to be particularly troublesome at the lower end of the cylinder bore l4 and at the upper end of the piston l5.

As a means for eliminating these sludge and varnish accumulations, I provide the rings 29, 30 and 3|. Each of these rings is preferably formed of metal and may be made either continuously circular in shape or rolled up from a strip with a single abutting ended joint. The ring 29 is given an arcuate or other shaped radial section to conform on its inner surface with the shape of the groove 21, and the rings 32 and 3| be cylindrical in shape as shown. The outer periphery of the piston l5 is relieved to receive the ring 30 with suflicient radial clearance so that ring 30 may have freedom to engage the cylinder bore l4, and similarly the cylinder bore H5 is relieved opposite the upper end of the piston to loosely receive the ring 3| with sufficient radial freedom of movement to engage the periphery, of the piston l5. Opposite ends of each of these rings are square cut to provide relatively sharp cutting edges 32 which effect a scraping engagement of the piston and cylinder surfaces and the removal therefrom of varnish and sludge deposits. Due to the looseness of flt of the rings in their grooves and the forces of their own inertia acting on them during engine operation, they undergo a substantial amount of shifting movement, both radially and axially of the lash adjuster cylinder, which movement causes their end edges to effect the desired cleaning of the piston and tappet surfaces. In order to insure that the ring 29 does not interfere with communication between the cylinder and piston ports 26 and 28, this ring is provided with a series of circumferentially spaced perforations 33.

In the modification of my invention shown in Figures 4 and 5, the piston groove 21 is omitted. I have also in this modification shown the upper and lower cleaning rings 3i? and Si omitted; however, it is understood that these may be incorporated in this form of my invention if desired. The function of the former piston groove 21 and its cleaning ring 29 is accomplished in this modification by increasing the number and preferably the size of the side ports in the piston and cylinder. As shown most clearly in Figure 5, I have provided two such side ports 50 in the cylinder l3 and three ports 5| in the piston IS. The ports 50 may be located diagrammatically opposite each other, and the piston ports 5| equally spaced circumferentially of the piston as shown. Other spacings of the ports may be employed and the number of the ports in each of the pistons and cylinders may be varied as desired, it being necessary only that a suitable diameter and spacing of the ports in ach be used as will insure at least one of the piston ports being open at all times to one of the cylinder ports. Preferably also each of the cylinder ports 50 terminates abruptly at its inner end with the bore of the cylinder IS in order to obtain a sharp port defining edge 52 which will. serve during relative reciprocation and rotation of the piston and. cylinder to scrape the outer periphery of the piston clean of any varnish deposits. Similarly the outer ends of piston ports 5| terminate at the periphery of the piston with sharp edges 53 which will have a cleaning action on the bore of the cylinder during operation.

I claim:

1. In a hydraulic tappet including a cylinder, a piston slidable in the cylinder and a body of fluid in endwise thrust transmitting relation therebetween, said piston and cylinder having registerable side ports through which fluid to supply said body may be passed, the said ports in one of the pistons and cylinders being sufficient in number to insure at least partial registry between respective ports in the piston and cylinder irrespective of relative angular rotation between the piston and cylinder.

2. In a hydraulic tappet including a piston slidable in the cylinder and a body of fluid in endwise thrust transmitting relation therebetween, said piston and cylinder having registerable side ports accommodating the passage of fluid for supplying said body, the registerable ends of said ports terminating abruptly with the respective slidably interengaged surfaces of the piston and cylinder whereby the port defining edges of each said surface effects a scraping action on the opposing slidable surface during relative movement between th piston and cylinder.

3. In combination with a hydraulic tappet having a cylinder and a piston with surfaces, in relatively rotatable and reciprocable sliding engagement with each other, fluid forming both a thrust transmitting body between opposing ends of the piston and cylinder and a lubricant between their said surfaces, said fiuid being composed in part of an ingredient tending to form a deposit on said surfaces at normal tappet operating temperatures, means for supplying said fluid from an external source to form said body in accordance with the operating requirements of the tappet, said means including a, fluid reservoir in the piston and a plurality of ports in the cylinder and piston connecting said reservoir to said source, the ports in the piston and the ports in the cylinder terminating in abrupt sharp edges of said surfaces, said ports being sufiicient in number to insure continuous communication between at least a, portion of one piston port and one cylinder port and to effect the cleaning of their opposed piston and cylinder surfaces over substantially the full circumference of the piston.

4. In a hydraulic lash take-up device for use between respective driving and driven means, a pair of telescopically associated members having side walls in longitudinally slidable and relatively rotatable engagement with each other and other walls in spaced apart opposed driving relation with each other, means for conducting hydraulic fluid to the space between said other walls including a plurality of ports in the side walls of each said member, said ports in one of the members being sufficient in number to insure registry between at least one thereof and one of said ports in the other member irrespective of the relative rotative positions of the members.

5. In a hydraulic lash take-up device between respective driving and driven means, a cylinder having side walls provided with a plurality of fluid inlet ports in circumferentially spaced relation, a hollow piston in the cylinder having side walls slidably and rotatably fitting said cylinder side Walls, said piston side Walls having a plurality of circumferentially spaced fluid inlet ports unequal in number to the number of said cylinder ports, said piston ports being of suincient size to insure at least one of their number being in registry with at least one of the cylinder ports for any relatively rotated position of the piston in the cylinder.

EUGENE B. ETCHELLS.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,108,952 Wales Sept. 1, 1914 1,289,795 Johnson Dec. 31, 1918 2,237,854 Voorhies Apr. 8, 1941 2,240,640 Ducate May 6, 1941 2,272,074 Voorhies Feb. 3, 1942 2,418,674 Steiner Apr. 8, 1947 2,580,380 Banker Jan. 1, 1952 

